Overload responsive alarm for drive motor



oct. 7, 195s Filed Feb. 5, 1957 c. H. SCOTT 2,855,101

OVERLOAD RESPONSIVE ALARM FOR DRIVE MOTOR I 4 Sheets-Sheet 1 Flq Fig. 2.

INVENTORV Charles H. Scott ATTOR EY OvERLOAD RESPONSIVE ALARM FOR DRIVE MOTOR Filed Feb. 5, 1957 C. H'. SCOTT Oct. 7, 1958 4 sheets-sheet 2 4 Sheets-Sheet 3 H Ill w mi Oct. 7, 1958' I OVERLOAD RESPONSIVE ALARM FOR DRIVE MOTOR Filed Feb. 5, 1957 o @J Ml C. H. SCOTT Oct. 7, 1958 OVERLOAD REsPoNsIvE'ALARn/I FOR DRIVE MOTOR Filed Feb. 5, 1957 4 Sheets-Sheet 4 N @E Rm l s T Es C v w mm /m Y B A Illllltlll.

ATToR Y United States Patent OVERLOAD RESPONSIVE ALARM FOR DRIVE MOTOR Charles H. Scott, South Norwalk, Conn., assignor to Dori Oliver Incorporated, Stamford, Conn., a corporation of Delaware This invention relates to powered reduction gear drive mechanism with overload-responsive means adapted to actuate an alarm or else to effect stoppage of the drive motor.

Although in no limiting sense, this invention is herein shown embodied in a settling tank of the center pier type in which a solids carrying feed liquid upflowingthrough the hollow central pier is admitted centrally at the top of the tank while clarified liquid overows at the periphery, and a rotary raking structure turnably supported by the pier `conveys a sludge load of settled solids over the tank bottom toward the center of the tankfor discharge.

Hence," in a more specific sense, this invention relates to an improved combination of; a powered reduction gear drive mechanism for the rotary rake structure, with overload-responsive'means.

The drive mechanism here considered is of the torque- .balanced kind, in which a large bull gear is driven simultaneously at a plurality of points of its periphery, and in such a manner that interbalanced shares of the drive torque be imparted to respective drive pinions engaging the bull gear, with the result that power requirements as well as wear and tear upon the mechanism are minimized. Applying the driving torque to the periphery of the bull gear in a balanced manner is desirable and important because of the slow rate of rotation of the raking structure especially where large diameter sedimentation units are concerned, and in view of the high tooth pressures that would otherwise arise between a bull gear and a driving pinion. v

The object of thisfinvention is to provide simple drive mechanism capable of applying `a true or balanced drive torque to the rake structure, jointly with providing overload-responsive means that are sensitively and positively adjustable in order that they may become eective substantially at the exact overload anticipated.

The signicance of that objective will be appreciated in view of the fact vthat` heretofore the conditions for providing accurate over1oadresponsive means were contrary to and not reconcilable with those conditions that would provide a` balanced torque. It is axiomatic that in order to register overload accurately the overloadresponsive mechanism must be designed for directly and mechanically utilizing. the torque reaction of the drive mechanism itself, and such overload has been `known to Abe registered and utilized` through and from the actual =overladresponsive devices `as distinct from those of a idirectacting mechanical. nature. "criteria are not. positive :mdnot very satisfactory, nor

Indirect electrical 2,855,10l Patented Oct. 7, 1958 are they reliably adjustable to respond correctly at predetermined overloads upon the rake structure, compared with the much more positive and accurate criteria of direct mechanical torque reaction forces.

This invention is applicabie advantageously to the rake drive mechanism `of large size sedimentation tanks of the center pier type, where heavy torque loads coincident with very slow rotation of the rake structure are involved. In that instance, the rake structure comprises a central cage portion surrounding the center pier, and rotatably supported thereon by an annular vertical thrust bearing atop the pier. Consequently, a self-contained drive mechanism is also mounted upon the top of the pier designed to engage and drive the large annular bull gear that is unitary with the rake structure, for rotating the same.

Torque-balanced drive mechanism for rotating such pier supported rake structure is known, for example, from the patent to Scott No. 2,086,394 which comprises a pair of drive pinions engaging the internally toothed bull gear at diametrically opposed points. These drive pinions are driven simultaneously through a pair of spur gear trains extending in opposite directions from a motor disposed centrally atop the: pier. The motor torque is transmitted to the gear trains by way of compensatory torque balancing means effective to transmit equal shares of the drive torque of the motor to the respective drive pinions having drive engagement with the bull gear.

Hence it is a more specific object to provide torquebalanced drive mechanism of great simplicity and compactness employing high reduction ratio of worm drive means instead of trains of spur gears, for rotating the bull gear in order to eifect a slow rotation of the rake structure, in combination with mechanically accurate noneleotrical and direct-acting overload-responsive means applicable irrespective of the kind or type of drive mechanism employed.

According to this invention, these objects are attainable by providing a drive mechanism in which the torque input shaft is driven from the motor through an endless although positive acting torque transmitting element such as an endless chain running over a pair of sprockets, while the motor itself is xed to an adaptor member which is movable upon a base. Thus the motor is movable or tiltable in a direction (zo-extensive with the plane dening the path of the endless chain, or else movable in a direction towards and away from the input shaft in a direction lying in a plane at right angles to this input shaft. When an overload occurs in the operation of the rake structure, the correspondingly increased pull exerted by the drive motor upon the taut portion of the endless drive chain will act to overcome adjustable spring pressure provided to bodily urge the motor away from the input shaft. This increased pull of the chain will'move or tilt the motor with its adaptor member to actuate a switch producing an alarm signal or effecting the stoppage of the drive motor.

In a practical embodiment, with the invention applied to the center pier type sedimentation tank, there is provided at the top of the pier a frame or platform having peripheral bearing means for rotatably supporting the internally toothed bull gear that is patr of the rotary raking structure which surrounds the pier.

Equal shares of drive torque are imparted to the bull gear simultaneously by a pair of drive pinions engaging the bull gear at diametrically opposed points thereof. Each pinion is driven directly by a worm gear drive unit located above and mounted upon the outer marginal portion of the platform structure, each worm gear and the associated drive pinion being operatively interconnected by a vertical shaft. Both worm drive units in turn are operatively interconnected by means of a common horizontal drive shaft. This shaft represents the 'ice aL... level of the liquid overflowing into a surrounding effluent torque input shaft of the drive mechanism, and extending diametrically of the bull gear, carrying at each end the respective worm element that is part of the respective worm gear unit. This torque input shaft is thus balanced with respect to the actual thrust exerted by the respective Worms.

This particular arrangement of the components of the drive mechanism relative to one another as well as relative to the supporting frame, has the added advantage that the major portion of the frame or platform structure remains unencumbered, and especially the central portion thereof unobstructed so that the hollow interior of the pier is readily accessible through a central opening in the frame clear of all driving mechanism. In this connection, it is to be noted that the common torque input shaft is sectionalized so that the intermediate portion thereof can be disconnected from the end portions, for the purpose of clearing the entire area between the two worm drive units for access to and inspection of the interior of the hollow pier below.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claim rather than by the description preceding it, and all changes that fall within the metes and bounds of the claim, or equivalents of such metes and bounds, are therefore intended to be embraced by the claim.

Figure 1 is a vertical sectional view of a sedimentation tank of the center pier type diagrammatically indicating the type of drive head for rotating the rake structure, and representing the environment for the invention associated with the drive mechanism.

Figure 2 is a geratly enlarged side view of the drive mechanism taken from Figure 1, although with a portion Vbroken away to show annular bearing means for supporting the rake structure.

Figure 3 is a further enlarged plan view of the drive mechanism taken on line 3 3 Iof Figure 2, with a small portion broken away for showing the annular bearing means for the rake structure.

Figure 4 is a still further enlarged plan view of the drive motor arrangement with overload-responsive devices, taken on line 4 4 of Figure 2.

Figure 5 is a vertical sectional view of the drive motor and associated overload-responsive device, the section being taken on line 5 5 of Figure 4.

Figure 6 is an end view of the detail motor mounting, taken on line 6 6 of Figure 5.

Figure 7 is a vertical sectional detailed view of the overload responsive device, taken on line 7 7 of Figure 5.

As an example of the environment of this invention there is shown in Figure 1 a large concrete sedimentation tank of the center pier type. A rotary rake structure is supported upon the center pier, which pier also carries selfcontained thereon the powered drive mechanism or drive head to effect rotation of the rake structure. According to this embodiment, the invention resides in the combination of the drive mechanism with overload-responsive devices characterized more particularly by the fact that these devices are actuated directly by the torque reaction .that manifests itself in bodily displacement of the drive ,through a horizontal influent duct 14 leading into a vertical duct 15 upwardly through the center pier 13. Hence, influent liquid passing outwardly through influent open,-

`ings 16 at the top end of the pier enters the body of quiescent liquid that is being held in the tank for the purpose of solids sedimentation, and defined by its overflow level A usual peripheral overflow Weir W determines the Y 4 receiving launder 17. A usual circular scum battle 18 is also indicated, together with a usual cylindrical influent well 19 surrounding the top end portion of the pier as well as the inuent feed openings 16 therein.

Atop the pier 13 there is mounted and anchored a frame or platform 19 in the form of a hollow annular casting to furnish operating support for a rotary rake structure 2@ as well as for a drive mechanism indicated at 21 and which mainly comprises a pair of Worm drive units 21a and 2lb coupled by a common worm shaft 22 which worm shaft in effect represents the torque input shaft of the drive mechanism. A drive motor M is mounted upon and carried by the one worm drive unit 2lb for driving the input shaft 22 by way of endless chain and sprocket means indicated at 23. An overload-responsive device O is associated with the base of motor M, all as will be presently described in detail and by reference to the enlarged detailed Fgures 2 to 7.

The drive mechanism 21 is mouned upon the frame 19 which in turn is anchored atop the pier 13 as indicated by anchor bolts Z4. This frame 19 is here shown to ,-be in the general form of a hollow annular casting having an inwardly turned ange 25 whereby it is anchored to the pier. A large annular bull gear 26 of the internally toothed kind surrounds the annular frame 19 and is rotatable thereon by means of an annular vertical thrust ball bearing 27 having a lower ball race 28 constituted by an annular shelf being part of the cast iron frame 19 and extending peripherally thereof as well as outwardly therefrom. The upper ball race designated by the numeral 29 is formed by the bull gear 27 itself.'

The annular ball gear 27 constitutes the'top end portion of the rake structure 20 which in turn further consists of a central vertical cage portion 30 fastened to the gear 27 as by means of brackets 31 formed thereon, and furthermore of the usual rake arms 32 in thev form of horizontal truss structures to which are fastened the conventional sludge conveying blades 33.

By way of example, for the purpose of this invention, the drive mechanism for the rake structure comprises a pair of drive pinions 34 and 35 engaging the bull gear 26 at diametrically opposed points thereof. These pinions 34 and 35 are driven by respective worm gear units 36 and 37 both of which units are in turn driven by a common worm shaft 38 which constitutes the aforementioned torque input shaft of the mechanism, which in Figure 1 was designated by the numeral 22. Because of the disposition of the worms at each end the torque input shaft 38 is self-balancing with respect to actual' thrust, thus imparting equal shares of drive torque to each of the Worm gear units 36 and 37 and thus to each of the drive pinions 34 and 35.

More specifically, the worm gear drive unit 36 comprises a housing 39 bolted to the frame 19 as at 39a. The gearing inside this housing 39 comprises a worm vgear 40 rotatable together with the associated pinion 34 through a vertical shaft 41, and a worm 42 meshing with worm gear 40 having a Worm shaft 43 rotatable in the housing 39.

The worm gear drive unit 37 similarly comprises a housing 44 bolted to a frame 19 as at 44a. The gearing inside this housing comprises a worm gear 45 rotatable together with the associated drive pinion 35 by Way of an interconnecting Vertical shaft 46, and a Worm 47 meshing with worm gear 45 and having a worin shaft 48 rotating in the housing 44.

The two worm shafts 43 and 48 are in axial alignment with each other and are interconnected by an intermedi- -.ate length of shafting 49 constituting with the worm shafts 43 and 48 the aforementioned common worm shaft 38 representing the torque input shaft of the mechanism.

The worm shaft 48 has an outer protruding free end 48a which has fixed thereon a sprocket S1. The common '.worm shaft 38 is driven by an endless chain element 50 running over the driven sprocket S1 from a drive sprocket S2 shown to be fixed upon the shaft 52 of drive motor M.

With more specific reference to the detail Figures 4, 5, 6 and 7 there will now be described the manner in which this drive motor M is combined with the overload-responsive device of this invention. The motor M has xed to the bottom thereof an adaptor member or plate 53 whereby it is tiltably mounted upon a base plate 54 which in turn is fixed upon or bolted to the top of the worm gear drive unit 37. In this way, the motor M is bodily tiltable about an horizontal axis A as represented by an axle S5 extending parallel to the torque output shaft 38 of the mechanism. The axle 55 is iixedly held in lugs 53a and 53h of the tiltable plate 53 -as indicated 'by a xing screw 55a. This axle 55 in turn is rotatable in bearing blocks 54a and 5417 of the stationary base plate 54.

In this way, the motor M is tiltable towards and away from the torque input shaft 38, the near side of the motor facing towards shaft 38, the far side facing away from that shaft. The motor M is normally spring-urged into an outer limit position such as defined by a set screw 56 provided at the far side of the motor. That is, a compression spring 57 is provided at the near side of the motor between the stationary base plate 54 and the tiltable plate 53 for bodily urging the motor into the far limit position defined by the set screw 56. An adjusting screw 57a is provided upon the tiltable plate 53 for the purpose of adjustably varying the precompression of the spring 57 and thereby varying the point at which it is desired to have the mechanism respond to overload.

The actual response to overload imposed upon the mechanism, which is the overload upon the rotary rake structure 20, is realized by the provision of suitable monitor means, such as an alarm producing switch, or by the provision of a power cutoff switch device designed to be actuated by the very tilting movement of the drive motor M and contained in a switch box 58 here sl own to be a part of the stationary base plate 54. Whereas there are conceivable various ways in which a direct mechanical operative relationship between the motor and the overload-responsive switch device can be realized in the sense of this invention, the present embodiment provides in the switch box 58 a stationary switch such as a micro-switch 59 (see Figure 7) together with a switch actuating arm 60 lixedly carried by the axle 55. Also xed upon the axle 55 is a stop-arm 61 carrying a stop member in the form of a set screw 62 adapted to hit an abutment 63 at the bottom of the switch box S8.

It is clear then that the extent of the bodily tilting movement of the drive motor M about the axis A is adjustable in both directions, namely at its outer end 6 by the set screw 56 of the tiltable plate 53 engaging the stationary abutment 56a, and at its inner end by the set screw 62 on stop-arm 61 to engage the stationary abutment 63 within the switch box 58.

I claim:

The combination of a drive mechanism for the piersupported rotary rake structure of a sedimentation tank, having a frame atop the pier, an annular internally toothed bull gear being part of the rake structure and surrounding said frame and rotatably mounted thereon, powered drive mechanism mounted upon said frame for imparting 'balanced torque to said bull gear comprising a pair of drive pinions engaging said gear at diametrically opposed points thereof together with balanced torque transmitting means effective to apply equal interbalanced shares of the driving torque simultaneously to the respective drive pinion-s, with overload-responsive means to become effective at the occurrence of an overload upon the rake structure; characterized thereby that the drive mechanism more specifically comprises a worm gear drive for each drive pinion, disposed above and mounted upon said frame, with a vertical shaft operatively interconnecting each pinion with a respective worm gear drive unit above, and a horizontal shaft extending across said frame and representing `a torque input shaft for the drive mechanism to interconnect the worms of said worm gear drive units in a manner whereby torque application to said yshaft will impart interbalanced shares of driving torque to said drive pinions, and further characterized thereby that said overload-responsive means comprise an endless drive chain element transmitting torque from said motor to said input shaft, an adaptor member fixed to said motor and movable therewith upon said frame toward and away from said input shaft in the direction of a prescribed path lying in a plane at right angles to said shaft, and adjustable spring means effective to urge the motor base normally in a direction away from the input shaft, and electric switch means mounted adjacent to said adaptor member and adapted to be actuated by said member being urged against spring pressure toward said input shaft by said chain at the occurrence of an overload upon the mechanism.

- References Cited in the le of this patent UNITED STATES PATENTS 2,086,394 Scott July 6, 1937 2,126,884 Hardinge Aug. 16, 1938 2,417,688 Jeffery Mar. 18, 1947 2,553,958 Chelminski et al. May 22, 1951 2,589,298 Scott Mar. 18, 1952 

